Axle weight and bridge formula calculator
Scaled your load? Make sure the axles and the bridge are legal before you leave the truck stop.
How to use it
Enter the steer, drive and trailer weights from your scale ticket and your axle spacing. The tool checks the federal interstate limits: 80,000 lb gross, 34,000 lb per tandem and the bridge formula W = 500 × (LN/(N−1) + 12N + 36), rounded to the nearest 500 lb as in FHWA's bridge table. Two tandems spaced 36 feet or more apart can carry 34,000 lb each.
States can set different limits on non-interstate roads and for permitted loads, so check the state rules for your route.
Questions carriers ask
What is the federal bridge formula?
A formula that limits weight on groups of axles based on how many axles there are and how far apart they are, to protect bridges.
What's the max weight on a tandem?
34,000 lb on federal interstates, unless bridge spacing limits it further.